The film opens with townspeople discussing a 'curse' with the Frankenstein town council, in a continuation after the events of Son of Frankenstein (1939). Locals report that Ygor has survived. The council tells the citizens to do as they wish with the Frankenstein castle; the mob's response is to destroy it. Damaged caused to the structure uncovers the still-living monster from dried sulfur pits. Ygor takes the monster to Dr. Ludwig Frankenstein, who heals mental disease. Ygor threatens Ludwig with exposure if he refuses to heal the monster. Elsa discovers the diary of her grandfather, Baron Frankenstein; as she reads, scenes from the 1931 James Whale Frankenstein film are shown. Ygor and the monster break into Ludwig's estate, murdering Dr. Kettering in the process. Ludwig considers destr